package com.clark.io;

import java.io.FilterWriter;
import java.io.IOException;
import java.io.Writer;

/**
 * A Proxy stream which acts as expected, that is it passes the method calls on
 * to the proxied stream and doesn't change which methods are being called. It
 * is an alternative base class to FilterWriter to increase reusability, because
 * FilterWriter changes the methods being called, such as write(char[]) to
 * write(char[], int, int) and write(String) to write(String, int, int).
 * 
 * @author Stephen Colebourne
 * @version $Id: ProxyWriter.java 1003647 2010-10-01 20:53:59Z niallp $
 */
public class ProxyWriter extends FilterWriter {

    /**
     * Constructs a new ProxyWriter.
     * 
     * @param proxy
     *            the Writer to delegate to
     */
    public ProxyWriter(Writer proxy) {
        super(proxy);
        // the proxy is stored in a protected superclass variable named 'out'
    }

    /**
     * Invokes the delegate's <code>append(char)</code> method.
     * 
     * @param c
     *            The character to write
     * @return this writer
     * @throws IOException
     *             if an I/O error occurs
     * @since Commons IO 2.0
     */
    @Override
    public Writer append(char c) throws IOException {
        try {
            beforeWrite(1);
            out.append(c);
            afterWrite(1);
        } catch (IOException e) {
            handleIOException(e);
        }
        return this;
    }

    /**
     * Invokes the delegate's <code>append(CharSequence, int, int)</code>
     * method.
     * 
     * @param csq
     *            The character sequence to write
     * @param start
     *            The index of the first character to write
     * @param end
     *            The index of the first character to write (exclusive)
     * @return this writer
     * @throws IOException
     *             if an I/O error occurs
     * @since Commons IO 2.0
     */
    @Override
    public Writer append(CharSequence csq, int start, int end)
            throws IOException {
        try {
            beforeWrite(end - start);
            out.append(csq, start, end);
            afterWrite(end - start);
        } catch (IOException e) {
            handleIOException(e);
        }
        return this;
    }

    /**
     * Invokes the delegate's <code>append(CharSequence)</code> method.
     * 
     * @param csq
     *            The character sequence to write
     * @return this writer
     * @throws IOException
     *             if an I/O error occurs
     * @since Commons IO 2.0
     */
    @Override
    public Writer append(CharSequence csq) throws IOException {
        try {
            int len = 0;
            if (csq != null) {
                len = csq.length();
            }

            beforeWrite(len);
            out.append(csq);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
        return this;
    }

    /**
     * Invokes the delegate's <code>write(int)</code> method.
     * 
     * @param idx
     *            the character to write
     * @throws IOException
     *             if an I/O error occurs
     */
    @Override
    public void write(int idx) throws IOException {
        try {
            beforeWrite(1);
            out.write(idx);
            afterWrite(1);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(char[])</code> method.
     * 
     * @param chr
     *            the characters to write
     * @throws IOException
     *             if an I/O error occurs
     */
    @Override
    public void write(char[] chr) throws IOException {
        try {
            int len = 0;
            if (chr != null) {
                len = chr.length;
            }

            beforeWrite(len);
            out.write(chr);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(char[], int, int)</code> method.
     * 
     * @param chr
     *            the characters to write
     * @param st
     *            The start offset
     * @param len
     *            The number of characters to write
     * @throws IOException
     *             if an I/O error occurs
     */
    @Override
    public void write(char[] chr, int st, int len) throws IOException {
        try {
            beforeWrite(len);
            out.write(chr, st, len);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(String)</code> method.
     * 
     * @param str
     *            the string to write
     * @throws IOException
     *             if an I/O error occurs
     */
    @Override
    public void write(String str) throws IOException {
        try {
            int len = 0;
            if (str != null) {
                len = str.length();
            }

            beforeWrite(len);
            out.write(str);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>write(String)</code> method.
     * 
     * @param str
     *            the string to write
     * @param st
     *            The start offset
     * @param len
     *            The number of characters to write
     * @throws IOException
     *             if an I/O error occurs
     */
    @Override
    public void write(String str, int st, int len) throws IOException {
        try {
            beforeWrite(len);
            out.write(str, st, len);
            afterWrite(len);
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>flush()</code> method.
     * 
     * @throws IOException
     *             if an I/O error occurs
     */
    @Override
    public void flush() throws IOException {
        try {
            out.flush();
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invokes the delegate's <code>close()</code> method.
     * 
     * @throws IOException
     *             if an I/O error occurs
     */
    @Override
    public void close() throws IOException {
        try {
            out.close();
        } catch (IOException e) {
            handleIOException(e);
        }
    }

    /**
     * Invoked by the write methods before the call is proxied. The number of
     * chars to be written (1 for the {@link #write(int)} method, buffer length
     * for {@link #write(char[])}, etc.) is given as an argument.
     * <p>
     * Subclasses can override this method to add common pre-processing
     * functionality without having to override all the write methods. The
     * default implementation does nothing.
     * 
     * @since Commons IO 2.0
     * @param n
     *            number of chars to be written
     * @throws IOException
     *             if the pre-processing fails
     */
    protected void beforeWrite(int n) throws IOException {
    }

    /**
     * Invoked by the write methods after the proxied call has returned
     * successfully. The number of chars written (1 for the {@link #write(int)}
     * method, buffer length for {@link #write(char[])}, etc.) is given as an
     * argument.
     * <p>
     * Subclasses can override this method to add common post-processing
     * functionality without having to override all the write methods. The
     * default implementation does nothing.
     * 
     * @since Commons IO 2.0
     * @param n
     *            number of chars written
     * @throws IOException
     *             if the post-processing fails
     */
    protected void afterWrite(int n) throws IOException {
    }

    /**
     * Handle any IOExceptions thrown.
     * <p>
     * This method provides a point to implement custom exception handling. The
     * default behaviour is to re-throw the exception.
     * 
     * @param e
     *            The IOException thrown
     * @throws IOException
     *             if an I/O error occurs
     * @since Commons IO 2.0
     */
    protected void handleIOException(IOException e) throws IOException {
        throw e;
    }

}
